A Study to Compare the Results of FGFR Testing by Either ctDNA Blood Testing or Standard Tumor Tissue Testing

A new drug, erdafitinib, became available for some patients with bladder cancer that has spread to other organs. To qualify, patients must have specific genetic changes in their tumors. Currently, doctors use tumor tissue samples to check for these genetic changes, but these samples might not accurately reflect the current state of the patient's cancer. In this study, Investigators will test the patient's blood for these genetic changes in addition to the tumor tissue samples. It is thought that the blood test will give a more accurate result. Investigators hope this study will help to find out if more patients can benefit from erdafitinib than the ones identified by tissue testing only.